The present invention relates to detergent compositions and shampoos, and more particularly to those detergent compositions and shampoos which have relatively low ocular irritation and yet have large foam volume and improved foam stability.
Detergent compositions, like most types of liquid cleaning agents, generally comprise a mixture of one or more surfactants as the active ingredient, perfumes, coloring agents, thickeners, etc. The surfactants have two portions :1) hydrophobic hydrocarbon chain miscible with organic materials and 2) a hydrophilic end-group miscible with water. When such a surfactant contacts a particle of soil, the hydrocarbon chains mix therewith and the hydrophilic end-groups are presented to the aqueous solution. This process of emulsification allows the soil, which otherwise would resist removal by the water, to be cleaned from the body thereby. The surfactants may be classified as anionic, cationic, nonionic, or amphoteric, depending upon the character of the end-groups.
It is desirable that detergent compositions have high foam volume and foam stability, particularly if they are used as shampoos. The amount of foam or lather produced by a shampoo has a direct bearing on the perceived efficiency with which it cleans the hair. The stability of that foam indicates how long it will keep the hair lathered. Generally speaking, the larger the volume of foam produced and the more stable the foam, the more efficient the perceived cleaning action of the shampoo.
A further desirable property for a shampoo, especially one designed for use by children, is that it have low ocular irritation. Because a shampoo may accidentally contact the ocular mucosa during use, especially use by children, one which causes relatively little irritation is both desirable and useful. Such non-irritating shampoos are known, see for example Masci, et al., U.S. Pat. No. 3,055,836, but these generally have poor foam stability.
Surfactant betaines are generally known as amphoteric surfactants useful in detergent compositions. See, for example, U.S. Pat. No. 3,280,179, which teaches that high-lathering detergent compositions may be prepared by replacing some or all of the anionic or cationic surfactant in conventional shampoo formulations by the acyclic sulfobetaine disclosed therein or by incorporating the latter into conventional soaps. But while these compositions have large foam volume and foam stability, they are severe ocular irritants and hence are unsuitable for use by children or others who desire a non-irritating shampoo. Although a low-irritation, high foam shampoo comprising a betaine and other amphoteric surfactants has supposedly been suggested by Ceccarelli and Proserpio [Riv. Ital. Essenze, 59(9):573-577 (1971)], applicants' following of this teaching yielded a shampoo which is a severe ocular irritant. While applicants recognizes that the use of surfactant betaines in detergent compositions is taught by these publications, there is no suggestion of the formulations of the present invention, which combine high foam and good foam stability with low ocular irritation.